Maxim MAX5477 Dual, 256-tap, nonvolatile, i2c-interface, digital potentiometer Datasheet

19-3379; Rev 2; 12/04
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
The MAX5477/MAX5478/MAX5479 nonvolatile, dual,
linear-taper, digital potentiometers perform the function
of a mechanical potentiometer, but replace the
mechanics with a simple 2-wire digital interface. Each
device performs the same function as a discrete potentiometer or variable resistor and has 256 tap points.
The devices feature an internal, nonvolatile EEPROM
used to store the wiper position for initialization during
power-up. A write-protect feature prevents accidental
overwrites of the EEPROM. The fast-mode I2C-compatible serial interface allows communication at data rates
up to 400kbps, minimizing board space and reducing
interconnection complexity in many applications. Three
address inputs allow a total of eight unique address
combinations.
The MAX5477/MAX5478/MAX5479 provide three nominal resistance values: 10kΩ (MAX5477), 50kΩ
(MAX5478), or 100kΩ (MAX5479). The nominal resistor
temperature coefficient is 35ppm/°C end-to-end and
5ppm/°C ratiometric. The low temperature coefficient
makes the devices ideal for applications requiring a lowtemperature-coefficient variable resistor, such as lowdrift, programmable gain-amplifier circuit configurations.
The MAX5477/MAX5478/MAX5479 are available in 16pin 3mm x 3mm x 0.8mm thin QFN and 14-pin 4.4mm x
5mm TSSOP packages. These devices operate over
the extended -40°C to +85°C temperature range.
Features
♦ Power-On Recall of Wiper Position from
Nonvolatile Memory
♦ EEPROM Write Protection
♦ Tiny 3mm x 3mm x 0.8mm Thin QFN Package
♦ 35ppm/°C End-to-End Resistance Temperature
Coefficient
♦
♦
♦
♦
5ppm/°C Ratiometric Temperature Coefficient
Fast 400kbps I2C†-Compatible Serial Interface
1µA (max) Static Supply Current
Single-Supply Operation: +2.7V to +5.25V
♦ 256 Tap Positions per Potentiometer
♦ ±0.5 LSB DNL in Voltage-Divider Mode
♦ ±1 LSB INL in Voltage-Divider Mode
Functional Diagram
VDD
GND
HA
8-BIT
SHIFT
REGISTER
8
8
16-BIT
LATCH
Mechanical Potentiometer Replacement
Low-Drift Programmable-Gain Amplifiers
Volume Control
Liquid-Crystal Display (LCD) Contrast Control
256
WA
POR
SDA
SCL
I2C
INTERFACE
LA
16-BIT
NV
MEMORY
HB
8
WP
Applications
256
POSITION
DECODER
256
POSITION
DECODER
256
WB
MAX5477
MAX5478
MAX5479
A0
A1
A2
LB
†Purchase of I2C components from Maxim Integrated
Products, Inc. or one of its sublicensed Associated
Companies, conveys a license under the Philips I2C Patent
Rights to use these components in an I2C system, provided
that the system conforms to the I2C Standard Specification as
defined by Philips.
Ordering Information/Selector Guide
PART
TEMP RANGE
PIN-PACKAGE
END-TO-END
RESISTANCE (kΩ)
10
TOP
MARK
ABO
PACKAGE CODE
MAX5477ETE*
-40°C to +85°C
16 Thin QFN
MAX5477EUD*
-40°C to +85°C
14 TSSOP
10
—
T1633F-3
—
MAX5478ETE*
-40°C to +85°C
16 Thin QFN
50
ABP
T1633F-3
MAX5478EUD
-40°C to +85°C
14 TSSOP
50
—
—
MAX5479ETE*
-40°C to +85°C
16 Thin QFN
100
ABQ
T1633F-3
100
—
—
MAX5479EUD
-40°C to +85°C
14 TSSOP
*Future product—contact factory for availability.
Pin Configurations appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX5477/MAX5478/MAX5479
General Description
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
ABSOLUTE MAXIMUM RATINGS
SDA, SCL, VDD to GND .........................................-0.3V to +6.0V
All Other Pins to GND.................................-0.3V to (VDD + 0.3V)
Maximum Continuous Current into H_, L_, and W_
MAX5477......................................................................±5.0mA
MAX5478......................................................................±1.3mA
MAX5479......................................................................±0.6mA
Continuous Power Dissipation (TA = +70°C)
16-Pin Thin QFN (derate 17.5mW/°C above +70°C) 1399mW
14-Pin TSSOP (derate 9.1mW/°C above +70°C) .........727mW
Operating Temperature Range ...........................-40°C to +85°C
Maximum Junction Temperature .....................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VDD = +2.7V to +5.25V, H_ = VDD, L_ = GND, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VDD = +5V, TA =
+25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DC PERFORMANCE (VOLTAGE-DIVIDER MODE)
Resolution
256
Taps
Integral Nonlinearity
INL
(Note 2)
±1
LSB
Differential Nonlinearity
DNL
(Note 2)
±0.5
LSB
±1
LSB
Dual Code Matching
End-to-End Resistance
Temperature Coefficient
R0 and R1 set to same code (all codes)
TCR
Ratiometric Resistance
Temperature Coefficient
Full-Scale Error
Zero-Scale Error
35
ppm/°C
5
ppm/°C
MAX5477
-3
MAX5478
-0.6
MAX5479
-0.3
MAX5477
3
MAX5478
0.6
MAX5479
0.3
LSB
LSB
DC PERFORMANCE (VARIABLE-RESISTOR MODE)
Integral Nonlinearity (Note 3)
Differential Nonlinearity (Note 3)
INL
DNL
Dual Code Matching
VDD = 3V
±3
VDD = 5V
±1.5
VDD = 3V, MAX5477, guaranteed
monotonic
±1
VDD = 3V, MAX5478
±1
VDD = 3V, MAX5479
±1
VDD = 5V
±1
R0 and R1 set to same code
(all codes), VDD = 3V or 5V
±3
LSB
LSB
LSB
DC PERFORMANCE (RESISTOR CHARACTERISTICS)
Wiper Resistance
RW
Wiper Capacitance
CW
End-to-End Resistance
2
RHL
(Note 4)
325
675
10
MAX5477
7.5
MAX5478
MAX5479
10
12.5
37.5
50
62.5
75
100
125
_______________________________________________________________________________________
Ω
pF
kΩ
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
(VDD = +2.7V to +5.25V, H_ = VDD, L_ = GND, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VDD = +5V, TA =
+25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
DIGITAL INPUTS
VDD = 3.4V to 5.25V
Input High Voltage (Note 5)
VIH
Input Low Voltage
VIL
(Note 5)
Output Low Voltage
VOL
ISINK = 3mA
WP Pullup Resistance
IWP
Input Leakage Current
ILEAK
VDD < 3.4V
2.4
V
0.7 x VDD
0.8
0.4
255
V
kΩ
±1
Input Capacitance
V
µA
5
pF
HA = 1kHz (0 to VDD), LA = GND,
LB = GND, measure WB
-80
dB
MAX5478
100
MAX5479
50
DYNAMIC CHARACTERISTICS
Crosstalk
3dB Bandwidth (Note 6)
Total Harmonic Distortion Plus
Noise
THD+N
H_ = 1VRMS, f = 1kHz, L_ = GND,
measure W_
kHz
0.003
%
TA = +85°C
50
Years
TA = +25°C
200,000
TA = +85°C
50,000
NONVOLATILE MEMORY RELIABILITY
Data Retention
Endurance
Stores
POWER SUPPLY
Power-Supply Voltage
Supply Current
VDD
IDD
2.70
Writing to EEPROM, digital inputs at
GND or VDD (Note 7)
Normal operation, digital WP = GND
inputs at GND or VDD
WP = VDD
5.25
250
400
15
20.6
0.5
1
V
µA
TIMING CHARACTERISTICS
(VDD = +2.7V to +5.25V, H_ = VDD, L_ = GND, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VDD = +5V,
TA = +25°C. See Figure 1.) (Notes 8 and 9)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
ANALOG SECTION
Wiper Settling Time (Note 10)
tWS
MAX5478
500
MAX5479
1000
ns
DIGITAL SECTION
SCL Clock Frequency
fSCL
400
kHz
Setup Time for START Condition
tSU:STA
0.6
µs
Hold Time for START Condition
tHD:STA
0.6
µs
_______________________________________________________________________________________
3
MAX5477/MAX5478/MAX5479
ELECTRICAL CHARACTERISTICS (continued)
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
TIMING CHARACTERISTICS (continued)
(VDD = +2.7V to +5.25V, H_ = VDD, L_ = GND, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VDD = +5V,
TA = +25°C. See Figure 1.) (Notes 8 and 9)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SCL High Time
tHIGH
0.6
µs
SCL Low Time
tLOW
1.3
µs
Data Setup Time
tSU:DAT
100
ns
Data Hold Time
tHD:DAT
0
SDA, SCL Rise Time
SDA, SCL Fall Time
tR
tF
Setup Time for STOP Condition
tSU:STO
Bus Free Time Between STOP
and START Condition
tBUF
Pulse Width of Spike Suppressed
tSP
Capacitive Load for Each Bus
Line
CB
Write NV Register Busy Time
0.9
µs
300
ns
300
Minimum power-up rate = 0.2V/µs
ns
0.6
µs
1.3
µs
50
ns
(Note 11)
400
pF
(Note 12)
12
ms
Note 1: All devices are production tested at TA = +25°C and are guaranteed by design and characterization for -40°C < TA < +85°C.
Note 2: The DNL and INL are measured with the potentiometer configured as a voltage-divider with H_ = VDD and L_ = GND. The
wiper terminal is unloaded and measured with a high-input-impedance voltmeter.
Note 3: The DNL and INL are measured with the potentiometer configured as a variable resistor. H_ is unconnected and L_ =
GND. For VDD = +5V, the wiper is driven with 400µA (MAX5477), 80µA (MAX5478), or 40µA (MAX5479). For VDD = +3V,
the wiper is driven with 200µA (MAX5477), 40µA (MAX5478), or 20µA (MAX5479).
Note 4: The wiper resistance is measured using the source currents given in Note 3.
Note 5: The devices draw current in excess of the specified supply current when the digital inputs are driven with voltages between
(VDD - 0.5V) and (GND + 0.5V). See Supply Current vs. Digital Input Voltage in the Typical Operating Characteristics.
Note 6: Wiper at midscale with a 10pF load (DC measurement). L_ = GND, an AC source is applied to H_, and the W_ output is
measured. A 3dB bandwidth occurs when the AC W_/H_ value is 3dB lower than the DC W_/H_ value.
Note 7: The programming current exists only during power-up and EEPROM writes.
Note 8: The SCL clock period includes rise and fall times (tR = tF). All digital input signals are specified with tR = tF = 2ns and
timed from a voltage level of (VIL + VIH) / 2.
Note 9: Digital timing is guaranteed by design and characterization, and is not production tested.
Note 10: This is measured from the STOP pulse to the time it takes the output to reach 50% of the output step size (divider mode). It
is measured with a maximum external capacitive load of 10pF.
Note 11: An appropriate bus pullup resistance must be selected depending on board capacitance. Refer to the I2C-bus specification document linked to this web address: www.semiconductors.philips.com/acrobat/literature/9398/39340011.pdf
Note 12: The idle time begins from the initiation of the STOP pulse.
4
_______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
WIPER RESISTANCE
vs. INPUT CODE
SUPPLY CURRENT
vs. TEMPERATURE
0.7
0.6
0.5
VDD = 5V
0.4
0.3
0.2
450
400
350
SDA
2V/div
300
250
200
W_
20mV/div
150
MAX5478
CL = 10pF
H_ = VDD
FROM TAP 00 TO TAP 04
100
VDD = 3V
50
0.1
0
0
-40
-15
10
35
60
0
85
32
64
96
128 160 192 224 256
WIPER TRANSIENT AT POWER-ON
TAP-TO-TAP SWITCHING TRANSIENT
WIPER TRANSIENT AT POWER-ON
MAX5477/78/79 toc05
MAX5477/78/79 toc04
SDA
2V/div
MAX5479
CW_ = 10pF
H_ = VDD
FROM TAP 00 TO TAP 04
1µs/div
INPUT CODE
TEMPERATURE (°C)
MAX5477/78/79 toc06
VDD
2V/div
W_
20mV/div
VDD
2V/div
W_
1V/div
MAX5479
TAP = 128
MAX5478
TAP = 128
400ns/div
4µs/div
2µs/div
INTEGRAL NONLINEARITY
vs. CODE (VDM MODE)
DIFFERENTIAL NONLINEARITY
vs. CODE (VDM MODE)
INTEGRAL NONLINEARITY
vs. CODE (VRM MODE)
MAX5478
0.2
MAX5478
0.2
0.1
0.3
MAX5477/78/79 toc08
0.3
MAX5477/78/79 toc07
0.3
MAX5478
0.2
INL (LSB)
0
0
0
-0.1
-0.1
-0.1
-0.2
-0.2
-0.2
-0.3
-0.3
-0.3
0
32
64
96
128 160 192 224 256
CODE
W_
1V/div
0.1
0.1
DNL (LSB)
INL (LSB)
MAX5477/78/79 toc03
MAX5477/78/79 toc09
SUPPLY CURRENT (µA)
0.8
TAP-TO-TAP SWITCHING TRANSIENT
MAX5477/78/79 toc02
0.9
500
WIPER RESISTANCE (Ω)
MAX5477/78/79 toc01
1.0
0
32
64
96
128 160 192 224 256
CODE
0
32
64
96
128 160 192 224 256
CODE
_______________________________________________________________________________________
5
MAX5477/MAX5478/MAX5479
Typical Operating Characteristics
(VDD = +5V, H_ = VDD, L_ = GND, TA = +25°C, unless otherwise noted.)
Typical Operating Characteristics (continued)
(VDD = +5V, H_ = VDD, L_ = GND, TA = +25°C, unless otherwise noted.)
0.06
0.04
0.12
0.08
INL (LSB)
0.02
0
-0.02
MAX5479
0.16
0.04
0
-0.04
-0.04
-0.08
-0.06
-0.12
-0.08
-0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
-0.02
-0.04
-0.06
-0.08
-0.10
-0.12
-0.14
-0.20
-0.10
32
64
96
0
128 160 192 224 256
32
64
96
128 160 192 224 256
0
0.04
0
-0.04
MAX5479
0.16
0.12
0.08
DNL (LSB)
INL (LSB)
0.08
0.04
0
-0.04
-0.08
-0.08
-0.12
-0.12
-0.16
-0.16
-0.20
-0.20
0
32
64
96
128 160 192 224 256
0
32
64
96
CODE
CROSSTALK vs. FREQUENCY (MAX5479)
-40
-50
-60
-20
-30
-40
-50
-60
-70
-70
-80
-80
-90
-90
-100
-100
0.1
1
10
FREQUENCY (kHz)
100
1000
CW_ = 10pF
TAP = 128
-10
CROSSTALK (dB)
-30
MAX5477/78/79 toc16
-20
CROSSTALK (dB)
0
MAX5477/78/79 toc15
CW_ = 10pF
TAP = 0
0.01
128 160 192 224 256
CODE
CROSSTALK vs. FREQUENCY (MAX5478)
6
128 160 192 224 256
0.20
MAX5477/78/79 toc13
MAX5479
0.12
-10
96
DIFFERENTIAL NONLINEARITY
vs. CODE (VRM MODE)
0.20
0
64
CODE
INTEGRAL NONLINEARITY
vs. CODE (VRM MODE)
0.16
32
CODE
CODE
MAX5477/78/79 toc14
0
MAX5479
DNL (LSB)
0.08
MAX5477/78/79 toc11
MAX5478
DIFFERENTIAL NONLINEARITY
vs. CODE (VDM MODE)
0.20
MAX5477/78/79 toc10
0.10
INTEGRAL NONLINEARITY
vs. CODE (VDM MODE)
MAX5477/78/79 toc12
DIFFERENTIAL NONLINEARITY
vs. CODE (VRM MODE)
DNL (LSB)
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
0.1
1
10
100
1000
FREQUENCY (kHz)
_______________________________________________________________________________________
10,000
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
MIDSCALE WIPER RESPONSE
vs. FREQUENCY (MAX5478)
MIDSCALE WIPER RESPONSE
vs. FREQUENCY (MAX5479)
CW_ = 10pF
0
2
1
0
-1
GAIN (dB)
-2
GAIN (dB)
MAX5477/78/79 toc18
1
MAX5477 toc17
2
-3
-4
CW_ = 50pF
-5
-1
-2
CW_ = 10pF
-3
-6
-4
-7
-8
-5
1
10
1000
100
0.1
1
THD+N vs. FREQUENCY
(MAX5478)
THD+N vs. FREQUENCY
(MAX5479)
10
MAX5477 toc19
MIDSCALE
MIDSCALE
1
THD+N (%)
1
0.1
0.01
0.1
0.01
0.0001
0.0001
1
10
0.01
100
0.1
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE (MAX5478)
0.2
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
MAX5477/78/79 toc22
0.3
0.5
END-TO-END RESISTANCE CHANGE (%)
0.4
0.4
0.3
0.2
0.1
0
-0.1
-0.2
35
TEMPERATURE (°C)
60
85
100
600
550
500
WP = GND
450
400
350
300
250
200
-0.3
150
100
-0.4
50
VCC = 5V
VCC = 3V
0
-0.5
10
10
SUPPLY CURRENT
vs. DIGITAL INPUT VOLTAGE
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE (MAX5479)
MAX5477/78/79 toc21
0.5
1
FREQUENCY (kHz)
FREQUENCY (kHz)
MAX5477/78/79 toc23
0.1
SUPPLY CURRENT (µA)
0.01
END-TO-END RESISTANCE CHANGE (%)
1000
0.001
0.001
-15
100
FREQUENCY (kHz)
10
-40
10
FREQUENCY (kHz)
MAX5477 toc20
0.1
THD+N (%)
CW_ = 50pF
-40
-15
10
35
TEMPERATURE (°C)
60
85
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
DIGITAL INPUT VOLTAGE (V)
_______________________________________________________________________________________
7
MAX5477/MAX5478/MAX5479
Typical Operating Characteristics (continued)
(VDD = +5V, H_ = VDD, L_ = GND, TA = +25°C, unless otherwise noted.)
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
MAX5477/MAX5478/MAX5479
Pin Description
PIN
NAME
FUNCTION
TSSOP
THIN QFN
1
15
HA
Potentiometer A High Terminal
2
14
WA
Potentiometer A Wiper Terminal
3
13
LA
Potentiometer A Low Terminal
4
12
HB
Potentiometer B High Terminal
5
11
WB
Potentiometer B Wiper Terminal
6
10
LB
Potentiometer B Low Terminal
7
9
WP
Write-Protect Input. Connect to GND to allow changes to the wiper position and the data stored
in the EEPROM. Connect to VDD or leave open to enable the write protection of the EEPROM.
8
7
GND
Ground
9
6
A2
Address Input 2. Connect to VDD or GND (see Table 1).
10
5
A1
Address Input 1. Connect to VDD or GND (see Table 1).
11
4
A0
Address Input 0. Connect to VDD or GND (see Table 1).
12
3
SDA
I2C Serial Data
13
2
SCL
I2C Clock Input
14
1
VDD
Power-Supply Input. Connect a +2.7V to +5.25V power supply to VDD and bypass VDD to GND
with a 0.1µF capacitor installed as close to the device as possible.
—
8, 16
N.C.
No Connection. Do not connect.
—
EP
EP
Exposed Paddle. Do not connect.
SDA
tBUF
tSU:DAT
tSU:STA
tHD:DAT
tLOW
tHD:STA
tSU:STO
SCL
tHIGH
tHD:STA
tR
tF
START
CONDITION
(S)
REPEATED START
CONDITION
(SR)
ACKNOWLEDGE
(A)
STOP
CONDITION
(P)
START
CONDITION
(S)
PARAMETERS ARE MEASURED FROM 30% TO 70%.
Figure 1. I2C Serial-Interface Timing Diagram
Detailed Description
The MAX5477/MAX5478/MAX5479 contain two resistor
arrays with 255 elements in each array. The MAX5477
has a total end-to-end resistance of 10kΩ, the
MAX5478 has an end-to-end resistance of 50kΩ, and
the MAX5479 has an end-to-end resistance of 100kΩ.
8
The MAX5477/MAX5478/MAX5479 provide access to
the high, low, and wiper terminals for a standard voltage-divider configuration. Connect H_, L_, and W_ in
any desired configuration as long as their voltages
remain between GND and VDD.
_______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
S256
R255
Analog Circuitry
S255
The MAX5477/MAX5478/MAX5479 consist of two resistor
arrays with 255 resistive elements; 256 tap points are
accessible to the wipers, along the resistor string
between H_ and L_. The wiper tap point is selected by
programming the potentiometer through the I2C interface. An address byte, a command byte, and 8 data bits
program the wiper position for each potentiometer. The
H_ and L_ terminals of the MAX5477/MAX5478/
MAX5479 are similar to the two end terminals of a
mechanical potentiometer. The MAX5477/MAX5478/
MAX5479 feature power-on reset circuitry that loads the
wiper position from the nonvolatile memory at power-up.
R254
S254
RW
256-POSITION
DECODER
W_
S3
WIPER
CODE 02h
R2
S2
R1
Digital Interface
S1
L_
Figure 2. Potentiometer Configuration
SDA
S
P
START
CONDITION
STOP
CONDITION
SCL
Figure 3. Start and Stop Conditions
SDA
0
START
MSB
1
0
1
The MAX5477/MAX5478/MAX5479 feature an internal,
nonvolatile EEPROM that stores the wiper state for initialization during power-up. The shift register decodes
the command and address bytes, routing the data to
the proper memory registers. Data written to a volatile
memory register immediately updates the wiper position, or writes data to a nonvolatile register for storage
(see Table 2).
The volatile register retains data as long as the device
is powered. Removing power clears the volatile register. The nonvolatile register retains data even after
power is removed. Upon power-up, the power-on reset
circuitry controls the transfer of data from the nonvolatile register to the volatile register.
A write-protect feature prevents accidental overwriting
of the EEPROM. Connect WP to VDD or leave open to
prevent any EEPROM write cycles. The wiper register
only updates with the value in the EEPROM when WP =
A2
A1
A0
NOP/W
ACK
LSB
SCL
Figure 4. Slave Address
_______________________________________________________________________________________
9
MAX5477/MAX5478/MAX5479
A simple 2-wire I2C-compatible serial interface moves
the wiper among the 256 tap points (Figure 2). A nonvolatile memory stores the wiper position and recalls
the stored wiper position upon power-up. The nonvolatile memory is guaranteed for 50 years for wiper
data retention and up to 200,000 wiper store cycles.
H_
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
Table 1. Slave Addresses
ADDRESS INPUTS
SLAVE ADDRESS
A2
A1
A0
GND
GND
GND
0101000
GND
GND
VDD
0101001
GND
VDD
GND
0101010
GND
VDD
VDD
0101011
VDD
GND
GND
0101100
VDD
GND
VDD
0101101
VDD
VDD
GND
0101110
VDD
VDD
VDD
0101111
VDD. Connect WP to GND to allow write commands to
the EEPROM and to update the wiper position from
either the value in the EEPROM or directly from the I2C
interface. Connecting WP to GND increases the supply
current by 19.6µA (max).
Serial Addressing
The MAX5477/MAX5478/MAX5479 operate as slave
devices that send and receive data through an I2C-/
SMBus™-compatible 2-wire serial interface. The interface uses a serial data access (SDA) line and a serial
clock line (SCL) to achieve bidirectional communication
between master(s) and slave(s). A master, typically a
microcontroller, initiates all data transfers to the
MAX5477/MAX5478/MAX5479, and generates the SCL
clock that synchronizes the data transfer (Figure 1).
The MAX5477/MAX5478/MAX5479 SDA line operates
as both an input and an open-drain output. The SDA
line requires a pullup resistor, typically 4.7kΩ. The
MAX5477/MAX5478/MAX5479 SCL line operates only
as an input. The SCL line requires a pullup resistor (typically 4.7kΩ) if there are multiple masters on the 2-wire
interface, or if the master in a single-master system has
an open-drain SCL output. SCL and SDA should not
exceed VDD in a mixed-voltage system, despite the
open-drain drivers.
Each transmission consists of a START (S) condition
(Figure 3) sent by a master, followed by the
MAX5477/MAX5478/MAX5479 7-bit slave address plus
the NOP/W bit (Figure 4), 1 command byte and 1 data
byte, and finally a STOP (P) condition (Figure 3).
Start and Stop Conditions
Both SCL and SDA remain high when the interface is
not busy. A master controller signals the beginning of a
transmission with a START condition by transitioning
SDA from high to low while SCL is high. The master
controller issues a STOP condition by transitioning the
SDA from low to high while SCL is high, when it finishes
communicating with the slave. The bus is then free for
another transmission (Figure 3).
Bit Transfer
One data bit is transferred during each clock pulse.
The data on the SDA line must remain stable while SCL
is high (Figure 5).
Acknowledge
The acknowledge bit is a clocked 9th bit that the recipient
uses to handshake receipt of each byte of data (Figure
6). Thus, each byte transferred effectively requires 9 bits.
The master controller generates the 9th clock pulse, and
the recipient pulls down SDA during the acknowledge
clock pulse, so the SDA line remains stable low during
the high period of the clock pulse.
Slave Address
The MAX5477/MAX5478/MAX5479 have a 7-bit-long
slave address (Figure 4). The 8th bit following the 7-bit
CLOCK PULSE FOR
ACKNOWLEDGMENT
START
CONDITION
SDA
SCL
1
2
8
NOT ACKNOWLEDGE
SCL
DATA STABLE,
DATA VALID
CHANGE OF
DATA ALLOWED
Figure 5. Bit Transfer
SDA
ACKNOWLEDGE
Figure 6. Acknowledge
SMBus is a trademark of Intel Corporation.
10
______________________________________________________________________________________
9
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
D14
D13
D12
D11
D10
D9
D8
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
S
SLAVE ADDRESS
0
COMMAND BYTE
A
A
P
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
NOP/W
Figure 7. Command Byte Received
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
HOW CONTROL BYTE AND DATA BYTE MAP INTO
MAX5477/MAX5478/MAX5479 REGISTERS
D15 D14 D13 D12 D11 D10
D9
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
D8
D7
D6
D5
D4
D3
D2
D1
D0
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
S
SLAVE ADDRESS
0
A
COMMAND BYTE
NOP/W
A
DATA BYTE
A
P
1 BYTE
Figure 8. Command and Single Data Byte Received
slave address is the NOP/W bit. Set the NOP/W bit low for
a write command and high for a no-operation command.
The MAX5477/MAX5478/MAX5479 provide three
address inputs (A0, A1, and A2), allowing up to eight
devices to share a common bus (Table 1). The first 4
bits (MSBs) of the MAX5477/MAX5478/MAX5479 slave
addresses are always 0101. A2, A1, and A0 set the next
3 bits in the slave address. Connect each address input
to VDD or GND to set these 3 bits. Each device must
have a unique address to share a common bus.
Message Format for Writing
Write to the MAX5477/MAX5478/MAX5479 by transmitting the device’s slave address with NOP/W (8th bit) set
to zero, followed by at least 1 byte of information
(Figure 7). The 1st byte of information is the command
byte. The bytes received after the command byte are
the data bytes. The 1st data byte goes into the internal
register of the MAX5477/MAX5478/MAX5479 as selected by the command byte (Figure 8).
Command Byte
Use the command byte to select the source and destination of the wiper data (nonvolatile or volatile memory
registers) and swap data between nonvolatile and
volatile memory registers (see Table 2).
Command Descriptions
VREG: The data byte writes to the volatile memory register and the wiper position updates with the data in the
volatile memory register.
NVREG: The data byte writes to the nonvolatile memory
register. The wiper position is unchanged.
NVREGxVREG: Data transfers from the nonvolatile
memory register to the volatile memory register (wiper
position updates).
VREGxNVREG: Data transfers from the volatile memory
register into the nonvolatile memory register.
Nonvolatile Memory
The internal EEPROM consists of a 16-bit nonvolatile
register that retains the value written to it prior to power
down. The nonvolatile register is programmed with the
midscale value at the factory. The nonvolatile memory
is guaranteed for 50 years for wiper position retention
and up to 200,000 wiper write cycles. A write-protect
feature prevents accidental overwriting of the EEPROM.
Connect WP to VDD or leave open to enable the writeprotect feature. The wiper position only updates with
the value in the EEPROM when WP = VDD. Connect WP
to GND to allow EEPROM write cycles and to update
the wiper position from nonvolatile memory or directly
from the I2C serial interface.
Power-Up
Upon power-up, the MAX5477/MAX5478/MAX5479
load the data stored in the nonvolatile memory register
into the volatile memory register, updating the wiper
position with the data stored in the nonvolatile memory
register. This initialization period takes 10µs.
______________________________________________________________________________________
11
MAX5477/MAX5478/MAX5479
D15
COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
Table 2. Command Byte Summary
ADDRESS BYTE
1
SCL CYCLE
NUMBER
2
3
4
5
6
7
COMMAND BYTE
8
START
(S) A6 A5 A4 A3 A2 A1 A0
9
DATA BYTE
10 11 12 13 14 15 16 17 18
ACK
(A)
19 20 21 22 23 24 25 26
27
ACK
ACK
TX NV V R3 R2 R1 R0
D7 D6 D5 D4 D3 D2 D1 D0
(A)
(A)
VREG
0
1
0
1 A2 A1 A0 0
0
0
0
1
0
0
0
1
D7 D6 D5 D4 D3 D2 D1 D0
NVREG
0
1
0
1 A2 A1 A0 0
0
0
1
0
0
0
0
1
D7 D6 D5 D4 D3 D2 D1 D0
NVREGxVREG
0
1
0
1 A2 A1 A0 0
0
1
1
0
0
0
0
1
D7 D6 D5 D4 D3 D2 D1 D0
VREGxNVREG
0
1
0
1 A2 A1 A0 0
0
1
0
1
0
0
0
1
D7 D6 D5 D4 D3 D2 D1 D0
VREG
0
1
0
1 A2 A1 A0 0
0
0
0
1
0
0
1
0
D7 D6 D5 D4 D3 D2 D1 D0
NVREG
0
1
0
1 A2 A1 A0 0
0
0
1
0
0
0
1
0
D7 D6 D5 D4 D3 D2 D1 D0
NVREGxVREG
0
1
0
1 A2 A1 A0 0
0
1
1
0
0
0
1
0
D7 D6 D5 D4 D3 D2 D1 D0
VREGxNVREG
0
1
0
1 A2 A1 A0 0
0
1
0
1
0
0
1
0
D7 D6 D5 D4 D3 D2 D1 D0
VREG
0
1
0
1 A2 A1 A0 0
0
0
0
1
0
0
1
1
D7 D6 D5 D4 D3 D2 D1 D0
NVREG
0
1
0
1 A2 A1 A0 0
0
0
1
0
0
0
1
1
D7 D6 D5 D4 D3 D2 D1 D0
NVREGxVREG
0
1
0
1 A2 A1 A0 0
0
1
1
0
0
0
1
1
D7 D6 D5 D4 D3 D2 D1 D0
VREGxNVREG
0
1
0
1 A2 A1 A0 0
0
1
0
1
0
0
1
1
D7 D6 D5 D4 D3 D2 D1 D0
Standby
The MAX5477/MAX5478/MAX5479 feature a low-power
standby mode. When the device is not being programmed, it enters into standby mode and supply current drops to 500nA (typ).
Applications Information
The MAX5477/MAX5478/MAX5479 are ideal for circuits
requiring digitally controlled adjustable resistance,
such as LCD contrast control (where voltage biasing
adjusts the display contrast), or for programmable filters with adjustable gain and/or cutoff frequency.
STOP NOTES
(P)
WIPER A
ONLY
WIPER B
ONLY
WIPERS
A AND B
ing and gain to the resistor-divider network made by
the potentiometer (Figure 9) or by a fixed resistor and a
variable resistor (see Figure 10).
Programmable Filter
Figure 11 shows the MAX5477/MAX5478/MAX5479 in a
1st-order programmable application filter. Adjust the
gain of the filter with R2, and set the cutoff frequency
with R3. Use the following equations to calculate the
gain (A) and the -3dB cutoff frequency (fC):
A = 1+
Positive LCD Bias Control
Figures 9 and 10 show an application where the
MAX5477/MAX5478/MAX5479 provide an adjustable,
positive LCD bias voltage. The op amp provides buffer-
fC =
R1
R2
1
2π × R 3 × C
5V
5V
H_
30V
30V
W_
MAX5477
MAX5478
MAX5479
MAX480
H_
VOUT
L_
MAX5477
MAX5478
MAX5479
MAX480
VOUT
W_
L_
Figure 9. Positive LCD Bias Control Using a Voltage-Divider
12
Figure 10. Positive LCD Bias Control Using a Variable Resistor
______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
V+
HA
R3
C
MAX410
7
6
MAX410
R1
2
HB
4
R1
R2 = RHL x D / 256
WHERE RHL = END-TO-END RESISTANCE
AND = D DECIMAL VALUE OF WIPER CODE
HB
WB
R2
1
8
V-
R2, R3 = RHL x D / 256
WHERE RHL = END-TO-END RESISTANCE
AND D = DECIMAL VALUE OF WIPER CODE
LA
HA
VOUT
3
MAX5477
MAX5478
MAX5479
1/2 MAX5477
WA
LA
VIN
MAX5477/MAX5478/MAX5479
5V
WA
1/2 MAX5477
R2
WB
LB
LB
Figure 11. Programmable Filter
Figure 12. Offset Voltage Adjustment Circuit
5V
IN
IN
V OUT1
OUT
OUT
HB
HA
MAX6160
MAX6160
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
WA
ADJ
R
GND
ADJ
GND
LA
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
WB
R
10kΩ
FOR THE MAX5477
R
50kΩ
VOUT_ = 1.23V x
FOR THE MAX5478
R
100kΩ
VOUT_ = 1.23V x
FOR THE MAX5479
R
VOUT_ = 1.23V x
VOUT2
WHERE R = RHL x D / 256
AND D = DECIMAL VALUE OF WIPER CODE
LB
Figure 13. Adjustable Voltage Reference
Offset Voltage and Gain Adjustment
Pin Configurations
TOP VIEW
VDD
SCL
SDA
A0
N.C.
HA
WA
LA
16
15
14
13
12 HB
1
MAX5477
MAX5478
MAX5479
2
3
11 WB
10 LB
4
9
5
6
7
8
A1
A2
GND
N.C.
THIN QFN
(3mm x 3mm)
WP
HA 1
14 VDD
WA
13 SCL
LA
2
3
HB 4
MAX5477
MAX5478
MAX5479
12 SDA
11 A0
WB 5
10 A1
LB 6
9
A2
WP 7
8
GND
TSSOP
(4.4mm x 5mm)
Connect the high and low terminals of one potentiometer of a MAX5477 between the NULL inputs of a
MAX410 and the wiper to the op amp’s positive supply
to nullify the offset voltage over the operating temperature range. Install the other potentiometer in the feedback path to adjust the gain of the MAX410 (Figure 12).
Adjustable Voltage Reference
Figure 13 shows the MAX5477/MAX5478/MAX5479
used as the feedback resistors in multiple adjustable
voltage reference applications. Independently adjust
the output voltages of the MAX6160 parts from 1.23V to
V IN - 0.2V by changing the wiper positions of the
MAX5477/MAX5478/MAX5479.
Chip Information
TRANSISTOR COUNT: 12,651
PROCESS: BiCMOS
______________________________________________________________________________________
13
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
12x16L QFN THIN.EPS
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
D2
0.10 M C A B
b
D
D2/2
D/2
E/2
E2/2
CL
(NE - 1) X e
E
E2
L
k
e
CL
(ND - 1) X e
CL
CL
0.10 C
0.08 C
A
A2
A1
L
L
e
e
PACKAGE OUTLINE
12, 16L, THIN QFN, 3x3x0.8mm
E
21-0136
1
2
EXPOSED PAD VARIATIONS
DOWN
BONDS
ALLOWED
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO
JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED
WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.20 mm AND 0.25 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220 REVISION C.
PACKAGE OUTLINE
12, 16L, THIN QFN, 3x3x0.8mm
21-0136
14
E
2
2
______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
TSSOP4.40mm.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
15 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX5477/MAX5478/MAX5479
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages.)
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